Process for recovery of copper from ores thereof



E. B. THORNHILL ET AL PROCESS FOR RECOVERY OF COPPER FROM OREs THEREOFDec. 9, 1924 1,518,828'

Filed Nov. 6, 19122 Ore Bins Feeders Crusers l'aw or Gyra'ory) OversizeUndevsnze Solveni (acid) To Sme-Pref Patented Dec. 9, 1921iu muren ENT,oFFlcg EDWIN' B. THORNBILL AND HECTOR G. S. ANDERSON, OF-HURLEY, NEWMEXICO, AS- SIGNOBS TO THOBNHILL-ANDEBSON COMPANY, OF MUSJOGEE,OKLAHOMA, 'A COR- PORATION OF OKLAHOMA.

PROCESS FOR RECOmY OF COPPER FROM CRES THEBEOF.

Application filed November 6, 1922.. Serial N90. 599,254.

To all whom t may concern.'

Be it known that we, EDWIN B. THORN- HILL and HECTOR G. S. ANDERSON,citizens of the United States, residing at Hurley, county of' Grant, andState of New Mexico, have invented a new and useful Process for Recoveryof Copper from Ores Thereof, of which the following is a specification.

This invention relates to the-recovery of copper from ores containingoxidized copper compounds as well as sulfides of copper. Nearly allcopper ores contain some copper in oxidized form, together with sulfidesof copper. The sulfide constituents are readily recoverable in an'economical manne-r by concentration by the flotation processes with orwithout gravity concentratlon. The oxidized constituents (carbonates,silicates, etc.) are recoverable by leaching o eration, followed byprecipitation or by lectrode deposition, provided the content' inoxidized vcopper is sufficiently high.4 In copper ores containingone-half ound up to fi-ve pounds, more or less acid so uble copper,(copper in the form of oxidized copper compounds), it would notordinarily be an economical procedure to provide A'any special methodfor recovering this acid soluble copper in addition to the gravityconcentration and flotation used for recovery of the sulfide copper.

That is to say, assuming that the sulfide content of the ore issufiicient to enable concentration by tables, etc., and byflotation tobe economically effected, it would not be economical to install andoperate additional apparatusl for carrying on a special process forrecovery of the oxidized content of the ore when it contains less thanfive ounds per ton of such co per in oxidize form. On the other hand, 1fno provision is made for special treatment of the ore, then using theordinary gravity concentration and flotation operation, not over twentyper cent of the oxidized copper content of the ore would generall berecovered, particularly if this oxidize or acid soluble copper is in theform of carbonates. The main object of the present invention is toprovide for economical recoveryof such l oxidized or acid soluble copperore along with the sulfide content of the ore, without involving anyconsiderable expense in addition to the ordinary expense of the gravityconcentration and flotation.

We have found that when the oxidized or acid soluble copper content ofthe ore is less than five pounds per ton, and when the ore has beencrushed by the use of grinding media consistin of metallic iron balls,rods, etc., that sufliclent metallic iron is transferred to the pulpproduced in the grinding apparatus, and consisting of finely divided oreand water, to precipitate the acid soluble copper, in case it is broughtinto solution in the pulp. We have discovered that the finely groundmetallic iron introduced into the pulp by the grindingmachines isefiicient for precipitating purposes, and that the copper soprecipitated is as amenable to recovery from the pulp by subsequentfiotation, as is that precipitated by say sponge iron, on account 'ofthe fact that it is so finely divided, probably mostly passing 200 mesh.According` to our invention, the ore is agitated in contact with acidafter it has been finely ground in apparatus. using iron grindingsurfaces or media so as to thereby eflect solution of the oxidized oracid soluble copper content and precipitation of copper from suchsolution in metallic form such precipitated copper being subsequentlyrecovered byv flotation along with the copper sulfide content of theore.

Accompanying drawing is a flow sheet illustrating one embodiment of theprocess. If the ore is ground to pass, say 65 mesh, it will then be asize which can be readily agitated by modern agitating equipment andalso be of a size which will be subject 1to comparatively quickdissolution of the copper valuesby sulfuric acid or other reagents caable of dissolvin copper in this erefore, this aci soluble copper can bequickly and readily dissolved in fifteen minutes, more or less, bysulfuric acid, so that practically all of the copper in the acid solubleform is dissolved in this time. From our experience, We have determinedthat 90% of the acid soluble couper in an ore of average grade isdissolved in the first ten minutes after the vacid is added.

Where rod mills and ball mills are used more or less, per ton of ore,yfrom the grinding media to the ore pulp. (This transferred iron is notcapable of removal from the pulp, to any considerable extent,` by`magneticl separation, on account of the fact that it is so very finelydivided. rl`ests have demonstrated that about five Der cent of thisfinely divided iron can be removed by magnetic separation.)

Since the amount of copper that can be precipitated from copper .sulfatesolution by a pound of pure iron is, theoretically, 1.12, the fivepounds of iron above stated should precipitate approximately 5.6 poundsof copper. l Therefore, it would not be necessary on an ore containingsay four pounds .of copper in acid soluble form, to add grinding media,so that the acid will have.

sufficient time .to dissolve the acid soluble copper. The agitation ofthe ore with acid may be effected in any suitable apparatus. ,On accountof the fact that the finelv divided iron is present in the ore atthe'tiine that the' acid is added to the` ore. more or less simultaneousdissolution of the copper values and precipitation .by the finelydivided' iron present, takes place. The coinparative speed of solutionof the acid soluble copper is so much greater than. the speed ofsolution of the metallic iron present by the sulfuric acid, that theacid will dissolve-:the copper with sufficient. speed so that'the ironwill not be -materiallv affected directly by the acid. Therefore,practically simultaneous solution and precipitation of the copper in afinely divided form. will take place in the agitating equipment.Limestone, in sufficient excess, is added at the end of the agitationperiod, in order to neiit'ralize any residual acid present and also toprecipitate any ferrie sulfate formed,

then .or subsequently, so that subsequent flotation of this 'pulp willtake place in a n eutral rather than an acid or alkaline solution, andprevent the re-solution of any copper by ferrie sulfate or acid. Thepulp in this condition is then transferred by ordinary means toeniulsifying and/or flotation` machines. oil being added in sufficientamounts for the purpose of thev operation of flotation. In this manner.a substantial recovery of the acid soluble copper can be made by a verysmall additional cost per ton of ore treated. which cost will beconstituted inainbv of the cost of agitation and flotation operation.

finely. divided metallic iron is particularlythe cost of acid, andthereby anew and I important improvement over present methods isinstituted.

The agitation of the pulp containing acid soluble copper, should alwaysprecede the le have found that this susceptible to .eflicieiit recovery7bv ordinary flotation, therefore, if the flotation operation precededthe agitating operation, the finely divided iron would be effectivelyremoved from the pulp and would not subsequently be valuable for theprecipitation To illustrate the economy of the described process, wewill assume an ore such as provided at the Santa Rita mines in NewMexico, having a tot-al content of 1.20% copper, of which 0.15% is inthe acid soluble form.

of the dissolved copper.

The amount. of sulfuric acid necessaryto dissolve this acid solublecopper and at the same tinie'satisfy the acid consuming'elements of theore itself during the time required for the operation, is a. function ofany particular ore under consideration. We have found that an averageore of the stated character, requires, during the short period of aitation, from six to ten pounds to satisfy t e acid consuming elementsin the Ore itself. Assuming that the orev under present considerationrequires six -pounds v'at 60 B. acid lper .ton of ore and adding to thisamount the six pounds of B.' acid required to dissolve the 0.15% orthree pounds of copper in the acid soluble form, the total amount of 60B. acid required per ton of ore will be twelve pounds. The amount ofacid consumption due to the ore itself is largely a function of the timeof agitation, or, in other Words` the time during which the acid is incontact with the ore. Since, as statedl before, we have found that 90%of the acid dissolved during the first.

soluble, copper is ten minutes of contact of the ore with the acid, itis desirable to extend this time as little .beyond ten minutes as ispossible. An average ore of the kind ab is not a great acid consumer,and the agitation period may be economically extended to from twenty tothirty minutes.

The accompanying flow sheet indicates the manner in which this variationfrom common practice will operate. It will be noted that the onlyvariation from common-Y ly accepted practice is the additin of the overeferred to,

copper solvent a siifiicient. length of time I ahead of the flotationmachines to permit efficient solution of the acid soluble copper,

precipitation of the copper (which is simultaneous with solution). andneutralization of the excess acid.

YWhat. we claim is:

1. The process of recovering copper from ores containing copper inoxidized form,

which consists in grinding the ore in the 13 presence of Water, by theaction of grinding media containing iron, to form a pulp containing thefinely divided ore and finely divided metallic iron, adding acid to theore to dissolve the oxidized copper content of the ore, such dissolvedcopper being then precipitated by the action of the said finely dividedmetallic iron, and then neutralizing the pulp and subjecting ittolflotation to concentrate the precipitated copper.

' 2. A process as set forth in claim 1, wherein limestone is used as theneutralizing agent for the pulp. after precipitation -of the coppertherein.

3. The process or recovering copper from ores containing sulfide copperalong with an oxidized copper content of less than five pounds per ton,which consists in grinding the ore with water by the action of irongrinding media, to form a pulp containing .the ore in finely dividedcondition and also containing finely divided iron, adding suflicientacid to the ore to dissolve the oxidized copper content and to satisfylthe acid consumption of the ore, aside from its copper content, duringthe time required for solution of such copper content, causingprecipitation of the dissolved copper by the finely divided iron presentas aforesaid, neutralizing the pulp and then subjecting it to flotationto concentrate the precipitated metallic copper along with the sulfidecopper in the pulp.

In testimony whereof We have hereunto subscribed our names thistwenty-seventh day of October. 1922.

EDWIN B. THORNHILL. HECTOR b'r. S. ANDERSON.

